It is conventional to test semiconductor integrated circuits (“ICs”) during manufacture to ensure the integrity of the ICs. In a testing technique known as wafer testing, wafer-mounted ICs (or dies) are tested by establishing electrical current between test equipment such as a tester [e.g., automatic test equipment (i.e., ATE)] and each IC (or die) on the wafer. An example component that may be used in wafer testing is a test board, for example, a multilayered printed circuit board (PCB) connected to the test equipment to transfer test signals between the test equipment and a he ICs to be tested. The PCB may be included in what is often referred to as a probe card or a probe card assembly.
The probe card includes probe elements (e.g., needles, prongs, pins, beams, etc.) arranged for contact with a series of electrical terminals (or contacts) located on a semiconductor wafer. Conventional probe cards generally include a substrate, such as a space transformer, located between the probes and the PCB and adapted to electrically connect the probes to contacts on the PCB. Example space transformers may be formed from a multi-layer ceramic or organic substrate and includes conductive traces extending along and/or through the various layers of the substrate. For example, the probes of the probe card may be mounted to electrically conductive, preferably metallic, bonding pads formed on the substrate, such as by conventional plating or etching techniques well known in the art of semiconductor fabrication.
Referring to FIG. 1, there is shown prior probe 10 (of a probe card assembly) supported on substrate 12. Probe 10 includes beam 14 having base end 16 and tip end 18 and contact tip 20 adjacent tip end 18. Contact tip 20 of probe 10 is adapted for contact with a terminal (or contact) located on a device under test (DUT). Probe 10 also includes post 22 located on an upper surface of substrate 12 (e.g., on a trace or a contact pad/terminal of substrate 12). Beam 14 of prior probe 10 is attached to post 22 (e.g., using a tape automated bonding (TAB) process). For example, post 22 of prior probe 10 is attached to a contact pad (not shown) located on substrate 12. As shown, post 22 supports beam 14 of probe 10 such that beam 14 is cantilevered from post 22. Accordingly, this type of probe is sometimes referred to as a cantilever probe. Cantilever probes are typically used for testing devices such as memory or logic devices, which include relatively large spacing between rows or columns of terminals, or devices having terminals located about a periphery of the device.
The probe-mounting surface (e.g., the surface of a space transformer) for a probe card assembly is typically maintained within a flatness tolerance to control the resulting position of contact tips 20 of the probes, which may number in the hundreds or more. Substantial planarity of the probe-mounting surface desirably promotes uniformity in contact tip position (i.e., desirably promotes a substantially coplanar arrangement for those portions of the probes adapted to contact a DUT such as contact tip 20 of FIG. 1). The probe-mounting surface for a probe card, however, is not perfectly flat. Accordingly, the DUT-contacting portions of multiple contact tips 20 will not be co-planar. Variations in the position of contact tips 20 may also result from other factors (e.g., dimensional variations in the posts, beams, and contact tips of the probes; non-linearity of the beams; etc.). The cantilevered construction of beam 14 of probe 10 is adapted to provide deflection (i.e., flex) at tip end 18 when transverse load is applied to contact tip 20, such as when force is applied to beam 14 during contact of contact tip 20 with a DUT. This flexing capability of beam 14 of probe 10 desirably accommodates the above-described non-planarity in the position of contact tips 20, as well as non-planarity in the position of terminals on a DUT being contacted by tips 20, thereby ensuring that an electrical connection is established between the DUT and each probe 10 of the probe card assembly.
The height of contact tip 20 of prior probe 10 is selected to account for the deflection of tip end 18 that is expected during testing operations. For example, if the anticipated maximum deflection of tip end 18 of beam 14 is 0.003 inches, contact tip 20 should project more than 0.003 inches from tip end 18. Otherwise, a DUT might be brought into contact with the base end 16 of beam 14. For similar reasons, post 22 should have a height that is greater than the maximum anticipated deflection of tip end 18 of beam 14 to prevent contact between tip end 18 and the probe-mounting surface of substrate 12.
The construction of the prior probe 10, including beam and post elements, has been provided to promote the above-described desired uniformity in the position of contact tips 20 for a probe card incorporating probe 10. As should be understood, however, a probe card incorporating prior probe 10 desirably includes posts 22 having upper surfaces that are substantially co-planar with each other in order to provide precise location of contact tips 20 (e.g., substantial planarity). Such planarity between posts 22, however, involves posts 22 being formed with substantially planar surfaces and that the placement of posts 22 onto substrate 12 maintain a substantially co-planar arrangement between posts 22. In practice, this is a difficult and time consuming process. Thus, it would be desirable to provide a more easily manufactured, cost-effective, probe for a probe card providing tips adapted for precise positioning within tight tolerances.